, it occurred just after 1:30 p.m., a little more than four miles underground.

Readings so close together sometimes indicate underground activity that isn't seismic, like mining operations, but Richard Carroll of the Geological Survey of Alabama said there aren't any mines in the area shaken in November and again on Wednesday.

"There are no underground coal mines or any other type in that area," Carroll said. "The closest one would be in Brookwood, Ala."